The invention relates to the field of connection detection circuits and more specifically to circuits which detect when a connection detection device is connected to an active communication device over a communication line.
Modern portable electronic equipment put high demands for power on portable power sources such as batteries. To reduce the power consumption of such equipment, circuits have been designed which detect when different features of the equipment are not required and power down those features.
The present invention relates to a connection detection circuit which detects when the connection detection circuit, which for example may be incorporated as part of an RS232 receiver circuit, is connected to another communication device and which sets the state of a control line in response thereto.
A circuit and a method are presented which allow for the detection of an active communication device connected to the circuit, as distinguished from an inactive communication device connected to the circuit or the absence of a communication device connected to the circuit. The invention relates to a method of determining the presence of an active driver in communication with a receiver input terminal. The method includes the steps of receiving a signal and generating an inactive detection signal in response to the signal. The method also includes the steps of switching either a first voltage or a second voltage onto a conductor in response to the inactive detection signal, delaying the propagation of the switched voltage, and producing the delayed switched voltage as an output signal. In one embodiment, the step of switching either a first or a second voltage includes activating, in response to the inactive detection signal, either a first switch to apply the first voltage or a second switch to apply the second voltage.
The invention further relates to a circuit for determining the presence of an active driver in communication with a receiver which has an input terminal and an output terminal. The circuit includes an inactive detection subcircuit which itself includes a first detection input terminal in electrical communication with the output terminal of the receiver, a second detection input terminal which can receive a reference voltage, and a detection output terminal. The circuit further includes a delay stage, which has a delay stage input terminal in electrical communication with the detection output terminal, and a delay stage output terminal which is the output terminal of the circuit. The delay stage generates a delay stage output signal that is presented at the delay stage output terminal in response to a signal from the driver which is received at the input terminal of the receiver.
The invention additionally relates to a circuit for determining the presence of at least one active driver of a plurality of drivers which are in communication with a respective one of a plurality of input terminals. Each of the input terminals is capable of receiving one of a plurality of input signals indicative of an active driver in electrical communication with a respective one of a plurality of receivers. The invention additionally includes a plurality of delay stages in serial electrical communication. Each of the delay stages has a delay stage input terminal in electrical communication with a respective one of the input terminals, and each delay stage has a delay stage output terminal. The circuit has an output terminal in electrical communication with the delay stage output terminal of the last one of the plurality of serially electrically communicating delay stages. The last one of the plurality of delay stage generates a circuit output signal which is presented at the circuit output terminal which is indicative of at least an active one of the plurality of drivers in response to signals from the drivers received at the plurality of receivers.
The invention still further relates to a circuit for determining the presence of at least one active driver which includes a first delay stage that includes a first signal input terminal which can receive a signal indicating the presence of an active driver in electrical communication with a first receiver and having a first output terminal, such that the first delay stage generates a first output signal at the first output terminal in response to the first input signal. The circuit also includes a last delay stage that includes a last signal input terminal which can receive a signal that can indicate the presence of an active driver in electrical communication with a last receiver, a last accumulated input terminal in electrical communication with the first output terminal of the first delay stage, and having a last output terminal. The last delay stage generates a last output signal at the last output terminal which indicates the presence of at least one active driver in electrical communication with a respective one of the receivers. In another embodiment, the circuit further contains at least one interim delay stage which has an interim signal input that receives an interim input signal indicative of the presence of an active driver in communication with an interim receiver, an interim accumulated input terminal in electrical communication with the output terminal of the first delay stage, and an interim output terminal, such that the interim output signal which is presented at the interim output terminal is responsive to the interim input signal and the signal received at the interim accumulated input terminal. In yet another embodiment, an inverter is in electrical communication with the last output terminal, such that the last output terminal and the inverter provide first and second output signals that are respectively logically complementary.
The invention yet additionally relates to a circuit for determining the presence of at least one active driver, including a plurality of receivers which can each respectively receive one of a plurality of input signals, and a plurality of inactive detection blocks, each inactive detection block in electrical communication with a respective one of the plurality of receivers and having an output terminal. The circuit further includes a plurality of delay stages, each of which is in electrical communication with a respective one of the inactive detection blocks, and each one of which is also in serial electrical communication with another of the plurality of delay stages. Each of the plurality of inactive detection blocks generates an inactive detection signal which appears at its output terminal in response to its respective input signal, and which is communicated to a respective one of the delay stages, such that a last delay stage generates a last output signal which is presented at the last output terminal that is indicative of the presence of at least one active driver in electrical communication with a respective one of the receivers.